Laser scanning method, laser irradiation device, and laser scanning program

ABSTRACT

A laser scanning method including emitting a pulsed laser beam from a distal end of an optical fiber in a liquid medium during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end, stopping emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of International Application PCT/JP2022/008752, with an international filing date of Mar. 2, 2022, which is hereby incorporated by reference herein in its entirety, and this application claims the benefit of priority to International Application PCT/JP2021/009531, filed Mar. 10, 2021, which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to laser scanning methods, laser irradiation devices, and laser scanning programs.

BACKGROUND ART

A known medical device in the related art scans a laser beam for treatment or imaging (e.g., see Non Patent Literatures 1 and 2). In Non Patent Literatures 1 and 2, an optical fiber is vibrated by an actuator to scan a laser beam emitted from the distal end of the optical fiber. In detail, Non Patent Literature 1 uses an electromagnetic actuator having a magnet bead fixed to the optical fiber and a solenoid disposed around the magnet bead. Non Patent Literature 2 uses a piezoelectric actuator having a piezoelectric element fixed to the optical fiber.

CITATION LIST Non Patent Literature {Non Patent Literature 1}

-   Layton A. Hall, two others, “Thulium fiber laser stone dusting using     an automated, vibrating optical fiber.”, Proceedings, Volume 10852,     Therapeutics and Diagnostics in Urology 2019, 108520C, Feb. 26, 2019

{Non Patent Literature 2}

-   Lee, C. M., four others, “Scanning fiber endoscopy with highly     flexible, 1 mm catheterscopes for wide-field, full-color imaging.”,     Journal of Biophotonics, Jun. 3, 2010, Volume 3, pp. 385-407

SUMMARY OF INVENTION

A first aspect of the present invention provides a laser scanning method including emitting a pulsed laser beam from a distal end of an optical fiber in a liquid medium during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end; stopping emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member. The laser scanning method further includes: changing a frequency of the pulsed laser beam; detecting movement of the optical fiber at each frequency; determining a resonance frequency of the optical fiber based on the detected movement; and determining a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency of the optical fiber.

Another aspect of the present invention provides a laser irradiation device including an optical fiber that emits a pulsed laser beam from a distal end thereof in a liquid medium; a processor having a hardware, the processor controlling the laser beam emitted from the optical fiber; and a movement detector that detects movement of the optical fiber, wherein the processor is configured to emit the pulsed laser beam from the distal end during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end, and wherein the processor is configured to stop emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member, wherein the processor is configured to: change a frequency of the pulsed laser beam; detect movement of the optical fiber at each frequency based on information from the movement detector; determine a resonance frequency of the optical fiber based on the detected movement; and determine a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency.

Another aspect of the present invention provides a storage medium storing a laser scanning program causing a laser irradiation device to execute: emitting a pulsed laser beam from a distal end of an optical fiber in a liquid medium during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end; stopping emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member, wherein the laser scanning program causes the laser irradiation device to execute: changing a frequency of the pulsed laser beam and detecting movement of the optical fiber at each frequency; determining a resonance frequency of the optical fiber based on the detected movement; and determining a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an overall configuration of a laser irradiation device and a laser treatment system according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of an optical fiber, an operation member, and a support member of the laser irradiation device in FIG. 1 .

FIG. 3 illustrates a process of how an optical fiber vibrates in accordance with emission of a pulsed laser beam.

FIG. 4 is a timing chart illustrating a laser-beam pulse group emitted from a distal end of the optical fiber.

FIG. 5A illustrates displacement of the vibrating optical fiber.

FIG. 5B illustrates a relationship between the position of the optical fiber and the emission timing of the laser beam.

FIG. 6 is a flowchart of a laser treatment method according to an embodiment of the present invention.

FIG. 7 illustrates a pulse-group repetition frequency, a pulse-group frequency, and the number of pulses.

FIG. 8A illustrates an optimal repetition cycle T3 corresponding to a maximum vibration amplitude.

FIG. 8B illustrates a time period T2 in FIG. 7 .

FIG. 9A is a partial view illustrating a configuration of a modification of the laser irradiation device.

FIG. 9B is a partial view illustrating a configuration of another modification of the laser irradiation device.

FIG. 9C is a partial view illustrating a configuration of another modification of the laser irradiation device.

FIG. 9D is a partial view illustrating a configuration of another modification of the laser irradiation device.

DESCRIPTION OF EMBODIMENTS

A laser scanning method and a laser irradiation device according to an embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1 , a laser irradiation device 1 according to this embodiment is applied to a laser treatment system 100 that treats a treatment target A by using a laser beam L. The laser treatment system 100 includes the laser irradiation device 1, an endoscope 10, and a display unit 20.

The endoscope 10 is, for example, a rigid or flexible ureteroscope and has a surgical-tool channel 10 a extending longitudinally through the endoscope 10. The endoscope 10 acquires an endoscopic image including a distal end 2 a (to be described later) of an optical fiber 2, inserted into the body via the surgical-tool channel 10 a, and the treatment target A.

The display unit 20 is a display device of any type, such as a liquid crystal display, and displays the endoscopic image acquired by the endoscope 10.

The laser irradiation device 1 includes the optical fiber 2, a tubular sheath (support member) 3 that supports the optical fiber 2, an operation member 4, a laser oscillator 5, a movement detector 6, a storage unit 7, and a processor 8.

FIG. 2 is a sectional view along a longitudinal axis of the sheath 3 and illustrates a configuration of the optical fiber 2, the sheath 3, and the operation member 4.

The optical fiber 2 is, for example, a single-mode fiber having a cladding diameter of 125 μm. The optical fiber 2 may be a multi-mode fiber or a double cladding fiber.

The sheath 3 is insertable into the surgical-tool channel 10 a. The optical fiber 2 extends through the sheath 3 in the longitudinal direction of the sheath 3, and the distal end of the optical fiber 2 protrudes from the distal end of the sheath 3.

A distal end 3 a of the sheath 3 is a support section that supports the optical fiber 2 at a position located at a base end side relative to a distal end 2 a of the optical fiber 2 with a distance. The inner diameter of the support section 3 a is smaller than the inner diameter of other sections of the sheath 3, and is equal to the outer diameter of the optical fiber 2 or slightly larger than the outer diameter of the optical fiber 2. Therefore, at the support section 3 a, the position of the optical fiber 2 is fixed in the radial direction. Accordingly, a vibration region 2 b of the optical fiber 2 which is disposed at a distal end side relative to the support section 3 a and which includes the distal end 2 a is supported in a cantilever manner by the sheath 3, and the vibration region 2 b can be vibrated in the radial direction of the optical fiber 2 about a part, acting as a fulcrum, of the optical fiber 2 in the support section 3 a.

The operation member 4 is a plate-shaped member disposed parallel to the vibration region 2 b and is fixed to the sheath 3. In the reference drawings, the surface at the optical fiber 2 side of the operation member 4 is a flat surface, but may alternatively be a surface having another shape, such as a curved surface.

The operation member 4 is disposed only at one side of the optical fiber 2 in the radial direction. As will be described later, the operation member 4 is provided for applying, to the distal end 2 a, a contraction force acting toward the operation member 4 during contraction of a bubble B generated at the distal end 2 a. The distance in the radial direction between the distal end 2 a at an initial position and the operation member 4 is designed such that the bubble B comes into contact with the operation member 4. In order to cause the bubble B to reliably come into contact with the operation member 4, the distal end of the operation member 4 is preferably disposed at a position where the distal end protrudes relative to the distal end 2 a of the optical fiber 2.

The laser oscillator 5 generates a pulsed laser beam L for treating the treatment target A. For example, the laser beam L is an infrared beam, and the laser oscillator 5 is a thulium fiber laser, a holmium YAG laser, a thulium YAG laser, an erbium YAG laser, a pulsed dye laser, or a Q-switch Nd YAG laser. The laser oscillator 5 is connected to the base end of the optical fiber 2 and supplies the laser beam L to the optical fiber 2. The laser beam L is emitted from the distal end 2 a toward the treatment target A.

The laser oscillator 5 is connected to a foot switch 9. The laser oscillator 5 generates the laser beam L and supplies it to the optical fiber 2 when the foot switch 9 is pressed.

When the laser irradiation device 1 is used for treating the treatment target A, the treatment target A is surrounded and covered by a liquid medium M, and the vibration region 2 b and the operation member 4 disposed outside the sheath 3 are disposed in the medium M. The medium M is a liquid, such as water, a physiological saline solution, a perfusate, a non-electrolytic solution, or a biological fluid like urine.

As shown in FIG. 3 , when the pulsed laser beam L is emitted from the distal end 2 a in the liquid medium M, the bubble B is generated at the distal end 2 a. The bubble B coming into contact with or close to the operation member 4 contracts, which induces movement of the vibration region 2 b toward the operation member 4. Consequently, the bubble B repeatedly forms and contracts, which vibrates the distal end 2 a in the radial direction.

In detail, when the emission of the laser beam L from the distal end 2 a starts, the laser beam L is absorbed by the medium M and therefore the temperature of the medium M increases, whereby the bubble B is generated at the distal end 2 a (t=t1).

While the laser beam L is being emitted, the bubble B grows and comes into contact with the operation member 4 (t=t2).

Then, when the emission of the laser beam L ends, the bubble B starts to contract, and the distal end 2 a moves closer toward the operation member 4 as the bubble B contracts (t=t3 and t4). Specifically, since only one side of the bubble B is in contact with the operation member 4, hydraulic pressure acts unevenly on the bubble B, thus causing the bubble B to contract toward the operation member 4. Accordingly, the distal end 2 a receives a contraction force F of the bubble B acting toward the operation member 4, so that the distal end 2 a moves closer toward the operation member 4.

Subsequently, the bubble B vanishes and the contraction force F dissipates (t=t5).

After the bubble B vanishes, a restoring force of the vibration region 2 b causes the distal end 2 a to move away from the operation member 4 (t=t6).

In addition to the case where the bubble B is in contact with the operation member 4, as in t=t2, t3, and t4, the bubble contraction force F acting toward the operation member 4 is applied to the distal end 2 a also in a state where the bubble B is not in contact with the operation member 4 since the operation member 4 exists near the bubble B.

As shown in FIG. 4 , the processor 8 controls the laser oscillator 5 to repeatedly emit a pulse group, including one or more pulsed laser beams L arranged in a time direction, from the distal end 2 a at a repetition frequency f1=1/T1. Moreover, the processor 8 sets the timing for emitting the pulse group from the distal end 2 a based on the repetition frequency f1, emits the pulse group from the distal end 2 a during a first period I and a third period III, and stops the emission of the laser beam L from the distal end 2 a during a second period II.

Each of the first period I and the third period III is the first half of one repetition cycle T1, and the second period II is the second half of one repetition cycle T1. In detail, the first period I is a period in which the optical fiber 2 at the initial position is moved closer toward the operation member 4 in accordance with contraction of the bubble B. The second period II is a period that is subsequent to the first period I or the third period III and in which the optical fiber 2 moves away from the operation member 4. The third period III is a period that is subsequent to the second period II and in which the optical fiber 2 moves closer toward the operation member 4.

The aforementioned pulse group is repeatedly emitted at the repetition frequency f1, so that the distal end 2 a vibrates in the radial direction at the repetition frequency f1, as shown in FIG. 5A, whereby the laser beam L emitted from the distal end 2 a is scanned in the radial direction. The repetition frequency f1 is set to a resonance frequency of the vibration region 2 b of the optical fiber 2 in accordance with calibration, to be described later.

In FIG. 4 , one pulse group includes three pulsed laser beams L. FIG. 5B illustrates the positions of the vibration region 2 b at time points ta, tb, and tc in FIG. 4 , as well as the position of the vibration region 2 b (see the hatched vibration region 2 b) from which the pulsed laser beam L is emitted from the distal end 2 a between the time point ta and the time point tb.

The movement detector 6 detects movement of the optical fiber 2 that is vibrating. The movement at least includes a vibration amplitude of the distal end 2 a of the optical fiber 2, and may further include a vibration frequency. In an example, the movement detector 6 has a vibration detection element 6 a fixed to the sheath 3. The vibration detection element 6 a is, for example, a vibration sensor, a pressure sensor, or a strain gauge. The vibration of the vibration region 2 b is transmitted to the vibration detection element 6 a via the support section 3 a so as to be detected by the vibration detection element 6 a. A detection signal output from the vibration detection element 6 a changes with the same frequency as the vibration frequency of the vibration region 2 b. The amplitude of the detection signal increases with increasing vibration amplitude of the distal end 2 a. Therefore, it is possible to detect a vibration frequency and a vibration amplitude of the optical fiber 2 based on the vibration frequency and the vibration amplitude of the detection signal.

The storage unit 7 has a memory, such as a RAM, and a nonvolatile, non-transitory computer-readable storage medium, such as a ROM or an HDD. The storage medium stores a laser scanning program therein.

The processor 8 has hardware, such as a central processing unit, and executes a laser scanning method, to be described below, in accordance with the laser scanning program.

Next, the laser scanning method according to this embodiment executed by the processor 8 will be described. FIG. 6 illustrates a laser treatment method using the laser irradiation device 1.

As shown in FIG. 6 , the laser treatment method according to this embodiment includes step S1 for disposing the optical fiber 2 and the operation member 4 within the body, step S2 to step S10 for calibrating frequencies f1 and f3 of the pulse group and the number of pulses, and step S11 for irradiating the treatment target A with the laser beam L from the laser irradiation device 1 while scanning the laser beam L. Step S2 to step S11 correspond to the laser scanning method according to this embodiment.

In step S1, the surgeon inserts the endoscope 10 into the body, such as the ureter, of a patient C, inserts the sheath 3 into the body via the surgical-tool channel 10 a together with the optical fiber 2 and the operation member 4, and disposes the vibration region 2 b and the operation member 4 outside the endoscope 2. The space surrounding the vibration region 2 b and the operation member 4 is filled with the liquid medium M.

Subsequently, the surgeon inputs a command to the laser irradiation device 1 by using, for example, an input unit (not shown), so as to cause the laser irradiation device 1 to execute the calibration in step S2 to step S10.

The calibration includes a first process (step S2 to step S6) for setting the pulse-group repetition frequency f1 and a second process (step S7 to step S10) for setting the pulse-group frequency f3 and the number of pulses.

As shown in FIG. 7 , the pulse-group repetition frequency f1 (=1/T1) is a repetition frequency of the pulse group. T1 indicates a repetition cycle of the pulse group. The pulse-group frequency f3 (=1/T3) is a repetition frequency of the pulsed laser beam L in one pulse group. T3 indicates a repetition cycle of the pulsed laser beam L. The number of pulses is the number of pulsed laser beams L included in one pulse group.

In the first process, the processor 8 causes the laser oscillator 5 to repeatedly generate the pulsed laser beam L, so that the pulsed laser beam L is repeatedly emitted from the distal end 2 a of the optical fiber 2 (step S2). Moreover, the processor 8 changes the pulse frequency of the laser beam L in a continuous or stepwise fashion (step S3).

In step S2 and step S3, the distal end 2 a vibrates synchronously with the pulse frequency of the laser beam L. The vibration amplitude of the distal end 2 a reaches a maximum when the pulse frequency matches the resonance frequency of the vibration region 2 b. The movement detector 6 detects movement including the vibration amplitude of the distal end 2 a at each frequency (step S4).

The processor 8 determines that the pulse frequency corresponding to the maximum vibration amplitude is the resonance frequency of the vibration region 2 b (step S5), and sets the pulse-group repetition frequency f1 to the resonance frequency (step S6).

Then, in the second process, the processor 8 changes the pulse-group frequency f3 and the number of pulses within a time period equivalent to half of the repetition cycle T1 in a state where the set repetition frequency f1 is fixed (step S7).

In step S7, the vibration amplitude of the distal end 2 a changes along with the changes in the pulse-group frequency f3 and the number of pulses. The movement detector 6 detects the movement including the vibration amplitude of the distal end 2 a at each pulse-group frequency and each number of pulses (step S8).

The processor 8 determines a combination of the pulse-group frequency and the number of pulses corresponding to the maximum vibration amplitude (step S9), and sets the pulse-group frequency f3 and the number of pulses in the pulse group in each of the first period I and the third period III to the determined pulse-group frequency f3 and the determined number of pulses (step S10).

FIGS. 8A and 8B illustrates an optimal repetition cycle T3 (=1/f3) and the optimal number of pulses corresponding to the maximum vibration amplitude.

As shown in FIG. 8A, the optimal repetition cycle T3 is equal to a time period from the time when the emission of the pulsed laser beam L starts to the time when the bubble B vanishes. In FIG. 8A, “ON” denotes a time period during which the laser beam L is emitted, and “OFF” denotes a time period during which the laser beam L is not emitted.

T2 denotes a time period from the start of emission of the first pulsed laser beam L to the start of emission of the last pulsed laser beam L in one pulse group. As shown in FIG. 8B, an optimal time period T2 corresponds to a time period from the time when the emission of the first pulsed laser beam L starts to the time when the bubble B first comes into contact with the operation member 4. The optimal number of pulses is (T2/T3)+1.

The movement of the optical fiber 2 detected in step S4 and step S8 may be displayed on the display unit 20. For example, the display unit 20 may display a graph indicating the relationship between the pulse frequency and the vibration amplitude, or may display the determined resonance frequency. Moreover, the display unit 20 may display a graph indicating the relationship among the pulse-group frequency, the number of pulses, and the vibration amplitude.

Next, in step S11, the surgeon presses the foot switch 9 to irradiate the treatment target A with the laser beam L from the distal end 2 a of the optical fiber 2, thereby performing a treatment on the treatment target A.

In step S11, the processor 8 controls the laser oscillator 5 to generate a pulse group having the frequencies f1 and f3 and the number of pulses set in step S6 and step S10. Accordingly, the distal end 2 a vibrates at the repetition frequency f1, whereby the laser beam L is scanned.

In detail, during the first period I corresponding to the first half of the first repetition cycle T1, the pulse group is emitted from the distal end 2 a, and the bubble B coming into contact with or close to the operation member 4 forms and contracts, which causes the distal end 2 a to move closer toward the operation member 4. During the subsequent second period II, the distal end 2 a moves away from the operation member 4, and the emission of the pulse group stops during that time.

During the third period III corresponding to the first half of the subsequent repetition cycle T1, the pulse group is emitted again from the distal end 2 a, and the bubble B coming into contact with or close to the operation member 4 forms and contracts, which causes the distal end 2 a to move closer toward the operation member 4. During the subsequent second period II, the distal end 2 a moves away from the operation member 4, and the emission of the pulse group stops during that time.

Subsequently, the emission of the pulse group in the third period III and the stoppage of the pulse group in the second period II are alternately repeated.

Accordingly, the laser irradiation device 1 according to this embodiment utilizes the contraction force F of the bubble B generated at the distal end 2 a of the optical fiber 2 as a driving force for vibrating the distal end 2 a. The bubble B is generated by the treatment laser beam L emitted from the distal end 2 a. Specifically, it is not necessary to add an actuator for driving the optical fiber 2 to the optical fiber 2. Thus, it is possible to reduce the diameter of a portion of the laser irradiation device 1 which is inserted into the body. Moreover, a function for scanning the laser beam L can be added to the laser irradiation device 1 without increasing the power consumption of the laser irradiation device 1.

In a case where an electromagnetic or piezoelectric actuator is used for vibrating the optical fiber 2, an electromagnetic field generated by the actuator may have an adverse effect on the endoscopic image. In this embodiment, the treatment laser beam L is an infrared beam, therefore an adverse effect on the endoscopic image can be prevented.

Furthermore, in order to crush a calculus efficiently, it is preferable that the scanning range of the laser beam L be wide. In this embodiment, the pulsed laser beam L is emitted from the distal end 2 a only during the first period I and the third period III in which the optical fiber 2 moves closer toward the operation member 4, and the emission of the laser beam L is stopped during the second period II in which the optical fiber 2 moves away from the operation member 4. Accordingly, the contraction force F is prevented from being applied in a direction opposite the moving direction of the distal end 2 a, that is, a direction that inhibits the vibration and thus causes the vibration amplitude to decrease, so that the distal end 2 a can be vibrated efficiently by the contraction force F.

Supposing that the pulsed laser beam L is emitted from the distal end 2 a during the second period II, the contraction force F acts on the distal end 2 a in the direction opposite the moving direction of the optical fiber 2. Thus, the contraction force F acts as a braking force against the vibration of the optical fiber 2, thus inhibiting an increase in the amplitude.

Furthermore, in this embodiment, the pulsed laser beam L is emitted multiple times from the distal end 2 a during the first period I and the third period III, and the bubble B forms and contrasts multiple times while the distal end 2 a moves closer toward the operation member 4. Accordingly, the contraction force F acts multiple times on the distal end 2 a, so that the vibration amplitude of the distal end 2 a and the scanning range of the laser beam L can be increased. As a result, the treatment efficiency of the treatment target A can be enhanced, thereby increasing, for example, the crushing volume of the calculus.

Because the resonance frequency of the vibration region 2 b varies between the air and the liquid medium M, it is difficult to accurately predict the resonance frequency of the vibration region 2 b in the usage environment. Furthermore, in order to obtain a vibration amplitude of the distal end 2 a required for scanning the laser beam L in the liquid medium M, it is important to cause the vibration region 2 b to resonate by matching the pulse-group repetition frequency with the resonance frequency of the vibration region 2 b.

According to this embodiment, the resonance frequency can be calibrated in a state where the vibration region 2 b is disposed in the treatment environment, so that the resonance frequency of the vibration region 2 b can be accurately measured in the treatment environment. Moreover, according to this embodiment, the pulse-group frequency f3 and the number of pulses are also calibrated in the state where the vibration region 2 b is disposed in the treatment environment. Accordingly, during the treatment, the vibration amplitude of the distal end 2 a and the irradiation range of the laser beam L can be maximized.

In the above embodiment, the optical fiber 2 and the operation member 4 are combined with each other by means of the sheath 3, and are inserted in the same surgical-tool channel 10 a. However, the configuration of the optical fiber 2 and the operation member 4 is not limited to this, and may be modified, where appropriate.

FIGS. 9A to 9D illustrate modifications of the laser irradiation device 1.

In FIG. 9A, the optical fiber 2 and the operation member 4 are separated from each other, and are inserted in the same surgical-tool channel 10 a. In this configuration, the distance between the distal end 2 a and the operation member 4 is changeable.

In FIG. 9B, the optical fiber 2 and the operation member 4 are separated from each other, and are inserted in different surgical-tool channels 10 a and 10 b.

In FIG. 9C, the operation member 4 is provided at the distal end of the endoscope 10 instead of the laser irradiation device 1. The operation member 4 may be accommodated in a hole 10 c provided at the distal end surface of the endoscope 10, and may be protrudable from the distal end surface of the endoscope 10.

In FIG. 9D, the operation member 4 is directly fixed to the optical fiber 2 and is combined with the optical fiber 2.

In the modification in FIG. 9D, the optical fiber 2 is supported in a cantilever manner by the operation member 4. The modifications in FIGS. 9A to 9C may be provided with a support member of any type that supports the optical fiber 2 in a cantilever manner about a fulcrum.

In the above embodiment, the movement detector 6 detects the movement of the optical fiber 2 by using the vibration detection element 6 a. Alternatively, the specific configuration of the movement detector 6 is not limited to this, and the movement may be detected by using other means.

In a modified embodiment, a movement detector 6 may detect, during the calibration, the movement based on an endoscopic image which is obtained by the endoscope 10 and which includes the distal end 2 a.

In another modification, the movement detector 6 may supply another laser beam as a measurement beam together with the laser beam L for treatment to the optical fiber 2, and may detect the measurement beam reflected at the treatment target A and returning via the optical fiber 2. The intensity of the measurement beam changes with time in accordance with the vibration amplitude and the vibration frequency of the distal end 2 a. The movement detector 6 can detect the movement of the optical fiber 2 based on the temporal change in the detected intensity of the measurement beam.

The present disclosure is advantageous in that a laser beam can be scanned in a liquid medium without having to add an actuator for driving an optical fiber to the optical fiber and without increasing the power consumption.

REFERENCE SIGNS LIST

-   -   1 laser irradiation device     -   2 optical fiber     -   2 a distal end     -   3 sheath (support member)     -   4 operation member     -   5 laser oscillator     -   6 movement detector     -   7 storage unit     -   8 processor     -   9 foot switch     -   10 endoscope     -   20 display unit     -   100 laser treatment system     -   A treatment target     -   B bubble     -   L laser beam 

1. A laser scanning method comprising: emitting a pulsed laser beam from a distal end of an optical fiber in a liquid medium during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end; stopping emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member, wherein the laser scanning method further comprises: changing a frequency of the pulsed laser beam; detecting movement of the optical fiber at each frequency; determining a resonance frequency of the optical fiber based on the detected movement; and determining a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency of the optical fiber.
 2. The laser scanning method according to claim 1, wherein the optical fiber moves away from the operation member by means of a restoring force of the optical fiber during the second period.
 3. The laser scanning method according to claim 1, further comprising: emitting the pulsed laser beam from the distal end during a third period subsequent to the second period, wherein the third period is a period for moving the optical fiber toward the operation member.
 4. The laser scanning method according to claim 1, wherein a pulse group including a plurality of the pulsed laser beams are emitted in the first period.
 5. The laser scanning method according to claim 4, further comprising: changing a pulse-group frequency of the pulse group and a number of pulses therein, the pulse-group frequency being a repetition frequency of the pulsed laser beams in the pulse group, the number of pulses being the number of the pulsed laser beams included in the pulse group; detecting movement of the optical fiber at each pulse-group frequency and at each number of pulses; and setting the pulse-group frequency of the pulse group and the number of pulses therein in the first period based on the detected movement.
 6. The laser scanning method according to claim 1, wherein a number of pulses is (T2/T3)+1, wherein the T3 indicates a time from start of the emission of the pulsed laser beam to vanishing of the bubble, and wherein the T2 indicates a time from a start of emission of a first pulsed laser beam in one pulse group to start of emission of a last pulsed laser beam in the one pulse group, wherein T2 indicates the time as a time from the start of the emission of the first pulsed laser beam in the one pulse group to a first contact between the bubble and the operation member.
 7. The laser scanning method according to claim 1, wherein the first period and the second period are alternately repeated.
 8. The laser scanning method according to claim 1, wherein the method increases a vibration amplitude of the distal end of the optical fiber by causing contraction force of the bubble to act on the distal end of the optical fiber multiple times by means of repeating, multiple times, the emission of the pulsed laser beam in the first period to repeat generation and contraction of the bubble.
 9. A laser irradiation device comprising: an optical fiber that emits a pulsed laser beam from a distal end thereof in a liquid medium; a processor comprising a hardware, the processor controlling the laser beam emitted from the optical fiber; and a movement detector that detects movement of the optical fiber, wherein the processor is configured to emit the pulsed laser beam from the distal end during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end, and wherein the processor is configured to stop emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member, wherein the processor is configured to: change a frequency of the pulsed laser beam; detect movement of the optical fiber at each frequency based on information from the movement detector; determine a resonance frequency of the optical fiber based on the detected movement; and determine a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency.
 10. The laser irradiation device according to claim 9, wherein the optical fiber moves away from the operation member by means of a restoring force of the optical fiber during the second period.
 11. The laser irradiation device according to claim 9, wherein the processor is configured to emit the pulsed laser beam from the distal end during a third period subsequent to the second period, and wherein the third period is a period for moving the optical fiber closer toward the operation member.
 12. The laser irradiation device according to claim 9, further comprising: a support member that supports the optical fiber in a cantilever manner; a laser oscillator that supplies the pulsed laser beam to the optical fiber; and a movement detector that detects movement of the optical fiber.
 13. The laser irradiation device according to claim 9, wherein the processor is configured to emit a pulse group including a plurality of the pulsed laser beams during the first period.
 14. The laser irradiation device according to claim 13, wherein the processor is configured to change a pulse-group frequency of the pulse group and a number of pulses therein, the pulse-group frequency being a repetition frequency of the pulsed laser beams in the pulse group, the number of pulses being the number of the pulsed laser beams included in the pulse group, and wherein the processor is configured to determine the pulse-group frequency of the pulse group and the number of pulses therein in the first period based on movement of the optical fiber at each pulse-group frequency and at each number of pulses.
 15. The laser irradiation device according to claim 9, wherein a number of pulses is (T2/T3)+1, wherein the T3 indicates a time from start of the emission of the pulsed laser beam to vanishing of the bubble, and wherein the T2 indicates a time from a start of emission of a first pulsed laser beam in one pulse group to start of emission of a last pulsed laser beam in the one pulse group, wherein T2 indicates the time as a time from the start of the emission of the first pulsed laser beam in the one pulse group to a first contact between the bubble and the operation member.
 16. The laser irradiation device according to claim 9, wherein the first period and the second period are alternately repeated.
 17. The laser irradiation device according to claim 9, wherein the method increases a vibration amplitude of the distal end of the optical fiber by causing contraction force of the bubble to act on the distal end of the optical fiber multiple times by means of repeating, multiple times, the emission of the pulsed laser beam in the first period to repeat generation and contraction of the bubble.
 18. A storage medium storing a laser scanning program causing a laser irradiation device to execute: emitting a pulsed laser beam from a distal end of an optical fiber in a liquid medium during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end; stopping emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member, wherein the laser scanning program causes the laser irradiation device to execute: changing a frequency of the pulsed laser beam and detecting movement of the optical fiber at each frequency; determining a resonance frequency of the optical fiber based on the detected movement; and determining a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency.
 19. The storage medium storing the laser scanning program according to claim 18, wherein a number of pulses is (T2/T3)+1, wherein the T3 indicates a time from start of the emission of the pulsed laser beam to vanishing of the bubble, and wherein the T2 indicates a time from a start of emission of a first pulsed laser beam in one pulse group to start of emission of a last pulsed laser beam in the one pulse group, wherein T2 indicates the time as a time from the start of the emission of the first pulsed laser beam in the one pulse group to a first contact between the bubble and the operation member.
 20. The storage medium storing the laser scanning program according to claim 18, wherein the first period and the second period are alternately repeated. 